Flappy Bird's takedown by its creator has given malware creators a new outlet to exploit unsuspecting users.

According to security firm Sophos, it has discovered several applications claiming to be Flappy Bird in third-party Android app marketplaces. The trouble, however, is that the games in some cases contain malware and in others force users to send a text message to a given number, effectively giving the malware creators all they need to potentially exploit users.

Another security firm, Trend Micro, also chimed in on the issue, saying that it has discovered "a bunch of fake Android Flappy Bird apps spreading online." Every one of those it has discovered so far are "apps that send messages to premium numbers, thus causing unwanted changes to victims' phone billing statements."

Flappy Bird has become a hot-button issue in the mobile world after the game soared to popularity and was subsequently taken down by its creator, Dong Nguyen. That was the opening malware creators needed, the security firms say, to take advantage of users who didn't have a chance to try out the game and want to see what all the hype is about.

Both Trend Micro and Sophos said that users shouldn't attempt to download anything calling itself Flappy Bird, since the original version is "dead." They also warned users to "be wary of apps from alternative markets."